{"id":"GHSA-2x8m-83vc-6wv4","summary":"Flowise: SSRF Protection Bypass (TOCTOU & Default Insecure)","details":"### Summary\nThe core security wrappers (secureAxiosRequest and secureFetch) intended to prevent Server-Side Request Forgery (SSRF) contain multiple logic flaws. These flaws allow attackers to bypass the allow/deny lists via DNS Rebinding (Time-of-Check Time-of-Use) or by exploiting the default configuration which fails to enforce any deny list.\n\n\n### Details\nThe flaws exist in `packages/components/src/httpSecurity.ts`.\n\nDefault Insecure: If process.env.HTTP_DENY_LIST is undefined, checkDenyList returns immediately, allowing all requests (including localhost).\n\nDNS Rebinding (TOCTOU): The function performs a DNS lookup (dns.lookup) to validate the IP, and then the HTTP client performs a new lookup to connect. An attacker can serve a valid IP first, then switch to an internal IP (e.g., `127.0.0.1`) for the second lookup.\n\n\n### PoC\nEnsure `HTTP_DENY_LIST` is unset (default behavior).\n\nUse any node utilizing secureFetch to access `http://127.0.0.1`.\n\nResult: Request succeeds.\n\n#### Scenario 2: DNS Rebinding\n\nAttacker controls domain attacker.com and a custom DNS server.\n\nConfigure DNS to return `1.1.1.1` (Safe IP) with TTL=0 for the first query.\n\nConfigure DNS to return `127.0.0.1` (Blocked IP) for subsequent queries.\n\nFlowise validates `attacker.com` -\u003e `1.1.1.1` (Allowed).\n\nFlowise fetches `attacker.com` -\u003e `127.0.0.1` (Bypass).\n\nRun the following for manual verification \n\n```ts\n// PoC for httpSecurity.ts Bypasses\nimport * as dns from 'dns/promises';\n\n// Mocking the checkDenyList logic from Flowise\nasync function checkDenyList(url: string) {\n    const deniedIPs = ['127.0.0.1', '0.0.0.0']; // Simplified deny list logic\n\n    if (!process.env.HTTP_DENY_LIST) {\n        console.log(\\\"⚠️  HTTP_DENY_LIST not set. Returning allowed.\\\");\n        return; // Vulnerability 1: Default Insecure\n    }\n\n    const { hostname } = new URL(url);\n    const { address } = await dns.lookup(hostname);\n\n    if (deniedIPs.includes(address)) {\n        throw new Error(`IP ${address} is denied`);\n    }\n    console.log(`✅ IP ${address} allowed check.`);\n}\n\nasync function runPoC() {\n    console.log(\\\"--- Test 1: Default Configuration (Unset HTTP_DENY_LIST) ---\\\");\n    // Ensure env var is unset\n    delete process.env.HTTP_DENY_LIST;\n    try {\n        await checkDenyList('http://127.0.0.1');\n        console.log(\\\"[PASS] Default config allowed localhost access.\\\");\n    } catch (e) {\n        console.log(\\\"[FAIL] Blocked:\\\", e.message);\n    }\n\n    console.log(\\\"\\\n--- Test 2: 'private' Keyword Bypass (Logic Flaw) ---\\\");\n    process.env.HTTP_DENY_LIST = 'private'; // User expects this to block localhost\n    try {\n        await checkDenyList('http://127.0.0.1');\n        // In real Flowise code, 'private' is not expanded to IPs, so it only blocks the string \\\"private\\\"\n        console.log(\\\"[PASS] 'private' keyword failed to block localhost (Mock simulation).\\\");\n    } catch (e) {\n        console.log(\\\"[FAIL] Blocked:\\\", e.message);\n    }\n}\n\nrunPoC();\n```\n\n\n### Impact\nConfidentiality: High (Access to internal services if protection is bypassed).\n\nIntegrity: Low/Medium (If internal services allow state changes via GET).\n\nAvailability: Low.","aliases":["CVE-2026-41272"],"modified":"2026-05-05T16:11:44.558570Z","published":"2026-04-16T21:51:00Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-04-16T21:51:00Z","nvd_published_at":"2026-04-23T20:16:15Z","cwe_ids":["CWE-367","CWE-918"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-2x8m-83vc-6wv4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41272"},{"type":"PACKAGE","url":"https://github.com/FlowiseAI/Flowise"}],"affected":[{"package":{"name":"flowise","ecosystem":"npm","purl":"pkg:npm/flowise"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.1.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-2x8m-83vc-6wv4/GHSA-2x8m-83vc-6wv4.json","last_known_affected_version_range":"\u003c= 3.0.13"}},{"package":{"name":"flowise-components","ecosystem":"npm","purl":"pkg:npm/flowise-components"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.1.0"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 3.0.13","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-2x8m-83vc-6wv4/GHSA-2x8m-83vc-6wv4.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L"}]}